Multimorbidity in Medicare is increasingly prevalent and costly. The proportion of Medicare fee-for-service (FFS) beneficiaries with 2+ chronic conditions remained stable at 67% in 1999-2011, but the number of beneficiaries with 4+ chronic conditions increased markedly from 24% to 36%. The 67% of beneficiaries with two or more chronic conditions incurred a disproportionate share of FFS expenditures in both 2008-2011, driven by higher inpatient and outpatient utilization rates. As a result of high prevalence and disproportionate costs of multimorbidity, identifying effective sustainable care models for MCC beneficiaries is a key priority for policymakers and practitioners. However, the search for effective care models for MCC beneficiaries remains elusive because substantial investments in Medicare demonstrations did not achieve significant improvements in care quality or Medicare expenditures. One aspect of care that has received scant attention in these prior efforts is the influence of continuity of medication management (COMM) on patient outcomes and expenditures. Receiving care from a single provider has been associated with better care experiences, fewer emergency room visits and fewer hospitalizations. However, the average Medicare beneficiary saw an average of 2 primary care physicians and 5 specialists in 2002 and the number of providers increased with the number of conditions. Thus, uncoordinated care provided by multiple providers may be a mechanism by which multimorbidity drives adverse health and economic outcomes of beneficiaries with multiple chronic conditions (MCC). Multiple providers increase the likelihood of multiple prescribers and fragmented medication management. This, in turn, can result in therapeutic omissions, polypharmacy, dangerous or duplicative prescriptions and adverse drug events, particularly for MCC beneficiaries. Optimal coordination of medications for MCCs requires ongoing monitoring, adjustment, and re-evaluation of care goals, which is most effective in a continuous longitudinal partnership between patients and providers. Improving Continuity of Medication Management (COMM) by reducing the number of prescribers to approximate a medication home may translate into better disease control and lower expenditures, particularly for MCC beneficiaries. There has been research on medication reconciliation that should occur when patients transition to outpatient care after a hospital discharge. However, there is surprisingly little information about variability in COMM across beneficiaries or the association between COMM and outcomes that are important to MCC stakeholders, such as adherence, disease control, and costs. In prior AHRQ-funded work (R21 HS019445, PI: Maciejewski) we found that the number of prescribers was more predictive of medication non-adherence, emergency room visits and hospital admissions by veterans than the number of cardiometabolic conditions themselves. It is important to validate this COMM construct and evaluate whether these prior results generalize to Medicare beneficiaries. We propose to leverage a novel, rich secondary data that links Medicare claims to lab results to evaluate the potential benefits of COMM in MCC beneficiaries to address three aims in a cohort of Medicare beneficiaries with 1-3 cardiometabolic conditions (diabetes, hypertension and/or dyslipidemia) that are highly prevalent individually and in combination: 1) Examine the association between number of prescribers and control of diabetes and dyslipidemia. H1: Beneficiaries with more prescribers will have worse disease control than beneficiaries with one prescriber. 2) Examine the association between number of prescribers and adherence to medications for diabetes, hypertension or dyslipidemia. H2: Beneficiaries with more prescribers will have lower adherence than beneficiaries with one prescriber. 3) Examine the association between number of prescribers and Medicare expenditures. H3: Beneficiaries with more prescribers will have higher expenditures than beneficiaries with one prescriber. The proposed study addresses our long-term objective of optimizing the health and quality of life of Medicare beneficiaries with MCC. This proposal is responsive to RFA-HS-14-001's objective to identify patient and system factors associated with better outcomes for MCC beneficiaries. Examining whether COMM is associated with medication non-adherence, disease control and Medicare expenditures may identify mechanisms by which multimorbidity drives adverse health and economic outcomes. If true, such findings would suggest that the MCC-outcomes gradient can be addressed by models of care that improve COMM.